Light-emitting diode

• US 9,472,719 B2
• Filed: 02/18/2015
• Issued: 10/18/2016
• Est. Priority Date: 02/18/2015
• Status: Active Grant

• Current Assignee: Epistar Corporation (Ennostar, Inc.)
• Original Assignee: Epistar Corporation (Ennostar, Inc.)
• Inventors: Peng, Yu-Ren, Hsu, Tzu-Chieh, Chen, Shih-I, Lee, Rong-Ren, Chung, Hsin-Chan, Liao, Wen-Luh, Lin, Yi-Chieh
• Primary Examiner(s): Wilson, Allan R
• Application Number:
  US14/625,156
• Publication Number:
  US 20160240731A1
• Time in Patent Office: 608 Days
• US Class Current: 1/1
• CPC Class Codes: H01L 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/105 with a resonant cavity structure
• CPC Class Codes: H01L 33/12 with a stress relaxation structure, e.g. buffer layer
• CPC Class Codes: H01L 33/30 containing only elements of Group III and Group V of the Periodic Table
• CPC Class Codes: H01L 33/38 with a particular shape
• CPC Class Codes: H01L 33/42 Transparent materials
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector

Abstract

A light-emitting diode, comprises an active layer for emitting a light with a phase and a peak wavelength λ in air, a reflector, a lower semiconductor stack between the active layer and the reflector, wherein the lower semiconductor stack comprises multiple semiconductor layers, and each of the multiple semiconductor layers has a refractive index ni, a thickness di and two sides each contacting adjacent layers to form two interfaces, wherein each interface has a phase shift when the light passes through the interface.

Claims

1. A light-emitting diode, comprising:

an active layer for emitting a light ray with a phase and a peak wavelength λ

in air;

an upper semiconductor stack on the active layer;

a reflector; and

a lower semiconductor stack between the active layer and the reflector,

wherein the lower semiconductor stack comprises multiple semiconductor layers, and each of the multiple semiconductor layers has a refractive index ni, a thickness di and two sides each contacting adjacent layers to form two interfaces,

wherein each interface has a phase shift when the light ray travels through the two interfaces along a same direction, and

wherein, for one of the multiple semiconductor layers traveled through by the light ray, the thickness di satisfies at least one of the following conditions of;

(i) if the two phase shifts are the same, then 0.8*((2m−

1)/2)*(λ

/ni)≦

di≦

1.2*((2m−

1)/2)*(λ

/ni), where m is a natural number; and

(ii) if the two phase shifts are different, then 0.8*((2m−

1)/4)*(λ

/ni)≦

di≦

1.2*((2m−

1)/4)*(λ

/ni), where m is a natural number.

2. The light-emitting diode according to claim 1, wherein the thickness di of the one of the multiple semiconductor layers is larger than one seventh of the peak wavelength λ

in air.

3. The light-emitting diode according to claim 1, wherein the lower semiconductor stack is made of p-type semiconductor material.

4. The light-emitting diode according to claim 1, wherein the multiple semiconductor layers comprise a confining layer on the active layer, a cladding layer on the confining layer and a contact layer on the cladding layer.

5. The light-emitting diode according to claim 4, wherein the two phase shifts of the two interfaces of the confining layer are the same.

6. The light-emitting diode according to claim 4, wherein the confining layer contacting two adjacent layers, and the confining layer has a refractive index between the refractive indices of the two adjacent layers.

7. The light-emitting diode according to claim 4, wherein the two phase shifts of the two interfaces of the cladding layer are different.

8. The light-emitting diode according to claim 4, wherein the cladding layer contacting two adjacent layers, and the cladding layer has a refractive index smaller than the refractive indices of the two adjacent layers.

9. The light-emitting diode according to claim 4, wherein the two phase shifts of the two interfaces of the contact layer are different.

10. The light-emitting diode according to claim 4, wherein the contact layer contacting two adjacent layers, and the contact layer has a refractive index larger than the refractive indices of the two adjacent layers.

11. The light-emitting diode according to claim 1, wherein each of the multiple semiconductor layers has a refractive index between 2.8 and 3.6.

12. The light-emitting diode according to claim 1, wherein the peak wavelength λ

in air is larger than 550 nm.

13. The light-emitting diode according to claim 1, wherein the reflector comprises a metal layer contacting the lower semiconductor layer.

14. The light-emitting diode according to claim 1, wherein the reflector comprises a dielectric layer contacting the lower semiconductor layer and the refractive index of the dielectric layer is smaller than that of the lower semiconductor stack.

15. The light-emitting diode according to claim 1, wherein the reflector comprises a transparent conductive layer contacting the lower semiconductor layer and the refractive index of the transparent conductive layer is smaller than that of the lower semiconductor stack.

16. The light-emitting diode according to claim 1, wherein a distance between the reflector and the active layer is between 250 nm and 1 μ

m.

17. The light-emitting diode according to claim 1, further comprising a substrate and bonding layer adhering the substrate and the reflector.

18. The light-emitting diode according to claim 4, further comprises a buffer layer between the contacting layer and the cladding layer.

19. The light-emitting diode according to claim 4, wherein the contact layer comprises GaP.